Electrotechnical device

ABSTRACT

An electrotechnical device is provided, having components connected by means of plug connections. The interior of the device is filled with a casting material. The device includes: a housing; arranged in the housing a first component which has at least one terminally-protruding contact pin; a second component which has a socket on which terminally-located contact plugs are provided for receiving the contact pins; and an insert in which the first component is arranged. The insert includes a secluded chamber which has an opening into which the socket of the second component is introduced. The chamber additionally includes a rear wall lying opposite the opening through which the contact pins are stuck into the contact plugs of the socket. An air-tight seal exists between the contact pins and the rear wall. The housing is filled with the casting material from an end lying opposite to the opening of the chamber.

The invention relates to an electrotechnical device.

Modern electrotechnical devices, e.g. measuring devices, have, as arule, a number of components. These components, e.g. sensors,electronics units, etc., are, in current times, preferably modularlyconstructed. A modular construction permits the device to be offered ina variety of different variants, without the necessity of having tostock all variants in sufficient quantities. Only the components, whichcan be combined as required, need to be stored. Moreover, a modularconstruction offers advantages during manufacture. Thus, a specialvariant of the device can be manufactured from the components in a veryshort time. Preferably, the components are connected together by simpleplug connections.

Frequently, it is necessary to fill a remaining internal space of thefinished device by casting a material thereinto, e.g. a silicone rubber,in order e.g. to prevent the penetration of moisture. To accomplishthis, the casting material is filled into the device in the liquidstate. Should the liquid material flow into the area of the electricalplug connections, the quality of an electrical connection between thecontacts to be connected by the plug connection can be degraded, or eveneffectively destroyed, by the casting material.

It is an object of the invention to provide a new electrotechnicaldevice having components connected by means of plug connections and aninner space filled with a casting material.

To this end, the invention resides in an electrotechnical device having

-   -   a housing,    -   arranged in the housing, a first component        -   which has at least one terminally protruding, contact pin,    -   arranged in the housing, a second component,        -   which has a socket, on which terminally-located, contact            plugs are provided for receiving the contact pins,    -   arranged in the housing, an insert,        -   in which the first component is arranged,        -   which has a secluded chamber,            -   which has an opening, into which the socket of the                component is introduced, and            -   which has a rear wall lying opposite the opening,                through which the contact pins are stuck into the                contact plug of the socket,    -   wherein an air-tight seal exists between the contact pins and        the rear wall, and    -   wherein the housing is filled with a casting material from an        end lying opposite to the opening of the chamber.

In an embodiment, the first component is an electronics unit.

In an embodiment, the second component is a sensor unit.

In a further development, the chamber is a two-component injectionmolded part, which is made of a plastic of low Shore hardness at thelocations where the contact pins pass through the rear wall.

In a further development, the rear wall of the chamber is self-sealingat the locations where the contact pins pass through the plastic of lowShore hardness.

Additionally, the invention resides in a method for the filling of anelectrotechnical device of the invention with a casting material,wherein

-   -   the device is set in an upright position, in which the opening        of the chamber is down and the rear wall of the chamber is up,        and    -   the casting material is introduced from above,    -   so that a plug connection existing in the interior of the        chamber between the contact pins and the contact plugs is        shielded by the chamber and a region of the plug connection        remains free of the casting material.

The invention and additional advantages will now be explained in greaterdetail on the basis of the figures of the drawing, in which an exampleof an embodiment is presented; equal elements are provided in thefigures with equal reference characters.

FIG. 1 shows an exploded view of an electrotechnical device;

FIG. 2 shows a section through the housing with two components connectedby a plug connection; and

FIG. 3 shows a section through the housing with the two components, withthe cutting plane rotated 90° with respect to the cutting plane used forFIG. 2.

FIG. 1 shows an exploded view of an electrotechnical deice of theinvention.

In the illustrated example of an embodiment, the device is anelectromechanical fill level sensor for determining and/or monitoring apredetermined fill level in a container. Such sensors are used in themeasurement and control technologies.

The device includes a housing 1. The housing 1 is constructed as ascrew-in piece with a threaded section 3 and a hexagonal head 5.

A cylindrical internal space of the housing 1 is hollow and closed at alower end by a membrane, or diaphragm, 7. Formed on membrane 7 are endsof two oscillation rods 9. By means of the screw-in piece, the filllevel sensor is so secured in an internally threaded opening of acontainer wall that the oscillation rods extend into the interior of thecontainer and come into contact with a fill substance located in thecontainer, when the fill substance reaches the predetermined fill level.

Located in the internal space are a first component 11 and a secondcomponent 13 of the electrotechnical device. The first component 11 isan electronic unit in the illustrated example of an embodiment. It iscomposed essentially of an electronic circuit arranged on two circuitboards 15. The first component 11 has at least one terminally-located,protruding contact pin 17. In the illustrated example, a plurality ofcontact pins 17 are arranged in two rows.

The second component 13 is e.g. a sensor unit. In the illustratedexample, the sensor unit includes an electromechanical transducer. Thisis composed e.g. of piezoelectric elements arranged in a stack. Theelectromechanical transducer contains an exciting transducer and areceiving transducer. When an alternating voltage is applied to theexciting transducer, it causes the membrane 7 to oscillate. Theoscillations are, in turn, transferred to the oscillation rods 9, sothat these execute oscillations perpendicularly to their longitudinalaxes. When mechanical oscillations act on the receiving transducer,these produce an electrical alternating voltage with the frequency ofthe oscillation.

The electronic unit contains an amplifier, which receives at the inputthe alternating voltage produced by the receiving transducer andtransmits at the output the amplified alternating voltage to theexciting transducer. Consequently, the mechanical oscillation systemformed by the membrane 7 and the oscillation rods 9 lies, via theelectromechanical transducers, in the feedback loop of the amplifier, sothat it excites itself to oscillations of an eigenresonance frequency.When the oscillation rods are not in contact with the fill substance,the eigenfreqency of the mechanical oscillation system is higher thanwhen the oscillation rods immerse in the fill substance. The electronicunit assigned to the sensor unit contains an additional, evaluatingcircuit, which determines, whether the frequency of the alternatingvoltage issued by the amplifier lies above or below a predeterminedthreshold value. If the frequency is above the threshold value, then theoscillation rods 9 are oscillating freely; if it is beneath, then theoscillation rods 9 are covered by fill substance.

The first and second components 11, 13 are both arranged in the housing1. The second component 13 includes a base element 18 and a socket 19formed thereon. The second component 13 includes a base element 18 and asocket 19 formed thereon. On the socket 19 are terminally-locatedcontact plugs 21, which are provided to receive the contact pins 17.

FIGS. 2 and 3 show two sections through the device of FIG. 1. Forclarity, the oscillation rods 9 are not shown in FIGS. 2 and 3. Thesections of FIGS. 2 and 3 are in cutting planes which are rotated 90°with respect to one another.

Housing 1 also contains an insert 23, which serves to receive the firstcomponent 11. In the illustrated embodiment, insert 23 has anessentially cylindrical section 25, into which the electronics unit isintroduced, through a terminal, first opening 27. A holder is providedin the cylindrical section 25 for the circuit boards 15.

The cylindrical section 25 is closed by a rear wall 29 at its end lyingopposite to the opening 27.

On the cylindrical section 25, on a side of the rear wall 29 facing awayfrom the opening 27, a secluded chamber 31 is formed. When the firstunit 11 is introduced into the insert 23, the contact pins 17 pierce therear wall 29 and protrude into the chamber 31. An air-tight seal isformed between the contact pins 17 and the rear wall 29.

The chamber 31 forms preferably a two-component injection molded part,which is made of a plastic of low Shore hardness at the locations wherethe contact pins 17 pass through the rear wall 29. Of course, thechamber can be an integral part of the insert 23, which then preferablyis constructed completely as a two-component injection molded part.

Preferably, in this two-component injection molded part, the rear wall29 of the chamber 31 is constructed of a plastic of low Shore hardnessat the locations where the contact pins 17 pass through. Such a softplastic surrounds the contact pins 17 tightly and is thereforeself-sealing in the area of the contact pins 17. This offers theadvantage that no extra measures are necessary for achieving anair-tight sealing. Alone the sticking of the contact pins 17 through therear wall effects the sealing.

The insert 23 is made e.g. of polycarbonate (PC) and suitable as softplastic is e.g. a thermoplastic polymer. In selecting the syntheticmaterial for the insert 23, one is relatively free. The choice of thesoft plastic is, however, limited to materials assuring an air-tightself-sealing where the contact pins 17 pass through.

The chamber 31 has, located opposite the rear wall 29, an opening 33,into which the socket 19 of the second component 13 is introduced. Atthe same time, the contact pins 17 are stuck through the rear wall 29lying opposite to the opening 33 and into the contact plugs 21 of thesocket 19.

The housing 1 is filled with a casting material from an end lyingopposite to the opening 33 of the chamber 31. The casting material isindicated in the figures by cross-hatching of horizontal, dashed lines.

Suitable as casting material is e.g. a gel-like two-component siliconerubber, which is liquid after the mixing of the two components and thenvulcanized by addition cross-linking.

The device is filled with casting material by placing the device in anupright position. In this procedure, the opening 33 of the chamber 31 isdown and the rear wall 29 of the chamber 31 up.

The casting material is filled in this position from above into thehousing 1. The designations up and down refer to the filling positionsshown in the drawings.

The casting material flows into the housing and moves through theopening 27 into the insert 23. This leads to the cylindrical region 25becoming completely filled with casting material. Additionally, castingmaterial flows outside, around the insert 23, and reaches in this way tothe base element 18 of the second component 13. To the extent that thebase element 18 has openings therefor, also interior spaces of the baseelement 18 can become filled with casting material.

The casting material fills the entire interior space of the deviceslowly, from below upwards, and seals the chamber 31 as it rises.

In contrast, no casting material can get into the chamber 31. Duringfilling of the casting material from above, the chamber 31 forms aprotective shell, on which the casting material flows externallydownwards.

No casting material can go through the opening 33, because the trappedair resists such. Same as in the case of a cup, which is immersed intowater with the opening down, the pressure of the trapped air also hereprevents the penetration of liquid. A sealing of the opening 33 is notrequired.

The electrical plug connection existing inside chamber 31 between thecontact pins 17 and the contact plugs 21 is shielded by the chamber 31.The region of the plug connection thus remains free of the castingmaterial.

Of course, the device can also have two or more plug connections betweenindividual components, which are kept free of casting material in themanner of the invention. For this, it is merely necessary to arrange theorientations of the individual chambers such that their rear walls pointin the same direction.

1-6. (canceled)
 7. Electrotechnical device, comprising: a housing; afirst component in said housing which has at least one terminallyprotruding contact pin; a second component in said housing which has asocket on which terminally-located contact plugs are provided forreceiving the contact pins; and an insert in said housing in which saidfirst component is arranged, which has a secluded chamber, an openinginto which said socket of said second component is introduced, and arear wall lying opposite said opening, through which the contact pinsare stuck into the contact plugs of said socket, wherein: an air-tightseal exists between the contact pins and said rear wall, and saidhousing is filled with a casting material from an end lying opposite tosaid opening of said chamber.
 8. The device as claimed in claim 7,wherein: said first component is an electronics unit.
 9. The device asclaimed in claim 7, wherein: said second component is a sensor unit. 10.The device as claimed in claim 7, wherein: said chamber is atwo-component injection molded part which is made of a plastic of lowShore hardness at the locations where the contact pins pass through saidrear wall.
 11. The device as claimed in claim 10, wherein: said rearwall of said chamber is self-sealing at the locations where the contactpins pass through the plastic of low Shore hardness.
 12. A method forthe filling of a device with a casting material, the device including ahousing, a first component, a second component, and an insert, the firstcomponent having at least one terminally protruding contact pin, thesecond component has a socket on which terminally-located contact plugsare provided, and the insert has a chamber, an opening and a rear wall,the method comprising the steps of: setting the device in an uprightposition, in which the opening of the chamber is down and the rear wallof the chamber is up; and introducing the casting material from above sothat a plug connection existing in the interior of the chamber betweenthe contact pins and the contact plugs is shielded by the chamber and aregion of the plug connection remains free of the casting material.